This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
In 3GPP long term evolution (LTE) the evolved NodeB (eNB) allocates physical layer resources for uplink (UL, to the eNB) and downlink (DL, from the eNB) shared channels. The physical layer resources include physical resource blocks (PRB) and a modulation coding scheme (MCS). The MCS determines the bit rate, and thus the capacity, of the PRBs. Allocations may be valid for one or more transmission time intervals (TTIs).
The use of semi-persistent scheduling (SPS) reduces the needed control channel signaling and thus the overall signaling overhead. As may be appreciated, if every resource allocation to a user equipment (UE) was individually signaled, the overhead could become unacceptably large. For example, in a voice over IP (VoIP) application, which can also be referred to as a VoLTE application, a DL frame could occur every 20 milliseconds. If each downlink frame were to be signaled individually the control channel bandwidth would need to be significantly increased. However, with SPS the eNB is enabled to establish an ongoing (persistent or semi-persistent) resource allocation for a UE that remains in place until changed. SPS can be used for both the UL and the DL.